1. Field of the Invention
The present invention relates to conductive films, electron emitting devices and image display apparatus that uses the conductive films.
2. Description of the Related Art
Conventionally, a general method for manufacturing surface conduction electron emitting devices involves subjecting a conductive film to an electrical current supply process called electrical current supply forming so that the electron emitting part is formed in the conductive film.
The applicant of the present invention proposes a method for forming a conductive film having an advantageous effect over a large area in the method for manufacturing surface conduction electron emitting devices. An example of such a method includes applying an organic-metal-containing liquid to the surface of a substrate by a spinner, forming a pattern of desired shape on the substrate, and decomposing the organic metal under heat, thereby obtaining a conductive film. In addition, Japanese Patent Application Laid-Open No. 8-171850 proposed a method for forming a conductive film of a desired shape by applying droplets of an organic-metal-containing liquid to the surface of the substrate by means of an inkjet.
The conductive film formed by the foregoing method is a film formed from fine particles of metal or metal oxide or a film in which fine particles are densely continuous.
By controlling the compositional materials and film thickness of the conductive film, the resistance of the conductive film is controlled so as to fall within a preferred range for an electron emitting device. From the point of view of electrical current supply forming and electron emission efficiency, it is necessary the range be from several nm to several tens nm.
Even if the film is thin, variation in the resistance of the conductive film must be restrained in order to stabilize electron emitting characteristics and restrain any variation in them. In addition, the conductive film must have sheet resistance as high as from 10 K to several hundred KΩ/
However, where the conductive film formed by the foregoing method is composed of metal as its main component and has a thickness of several nm or less, its resistance varies considerably and such a conductive film is not, therefore, suitable for practical use. Even if the film has a thickness of several nm or more and is stably resistant, its sheet resistance will be as low as several KΩ/ Likewise, where the film is composed of a metal oxide as its main component and has a thickness of several nm or less, resistance varies considerable, and, therefore, the film is not suitable for practical use. Even if the film has a thickness of several nm or more and is stably resistant, the resistance will be significantly affected by whether moisture or the like adheres to the surface of the film. Even if the film is baked in a vacuum for stabilization, part of the film will be deoxidized, which makes it impossible to stably obtain a conductive film of sheet resistance as high as from 10 K to several hundred KΩ/ Accordingly, electron sources in which more than one electron emitting devices are disposed suffer from the problem of large variation in electron emitting characteristics.
Even in an image display apparatus in which the electron source and a fluorescent substance are disposed opposite each other, variation in electron emitting characteristics leads to such problems as degradation in image quality.